Minimally invasive medicine, the practice of gaining access to a body vessel, duct, or organ using a wireguide to facilitate the subsequent introduction of other medical devices, has been evolving since the Seldinger technique was first popularized during the late 1950s and 1960s. The ability to exchange medical devices over a single indwelling wireguide without requiring displacement of the wireguide from the treatment site provided a significant advance. Using an “over the wire” exchange technique, a user could remove one medical device from the treatment site and advance another medical device to the site without losing access to the site provided by the wireguide. This technique provided greater control over positioning of medical devices and introduced efficiencies to minimally invasive treatment techniques.
“Over the wire” exchange techniques require the use of long wireguides because the user must be able to maintain control of the wireguide, independent of the device over the wireguide, at all times during an exchange. As a result, extremely long wireguides are typically used. For most techniques, a wireguide with a length that is at least double the length of the device being placed over the wire is used. These long wireguides may be viewed as cumbersome by some users.
The development of rapid exchange delivery systems and techniques allowed the use of shorter wireguides. In these systems, the wireguide and medical device, such as a catheter, are coupled to each other only along a portion of the length of the medical device. The wireguide exits a passageway of the medical device at a point between the proximal and distal end of the medical device via a port formed in a wall of the device. This allows the user to control the proximal end of the wireguide while removing a medical device placed along the wireguide. During removal, the coupled portion of the wireguide travels along the length of the wireguide, ultimately exiting the patient. At this point, the user can exchange medical devices by simply pulling the proximal end of the wireguide through the relatively short wireguide lumen of the device, and subsequently pass the proximal end of the wireguide through the wireguide lumen of a second medical device. Finally, the second device is advanced along the wireguide to the point of treatment. During the exchange, the wireguide position within the body vessel is maintained even though a relatively short length of wireguide extends outside of the patient.
Rapid exchange delivery systems and techniques have proven particularly desirable in coronary medicine where it is common for a sequence of procedures using multiple catheter-based devices to be performed over a single wireguide. For example, it is common to place multiple balloon-expandable stents in a body vessel following angioplasty. Rapid exchange delivery systems and techniques allow the placement of multiple stents without requiring withdrawal and replacement of the wireguide and without requiring the use of relatively long wireguides.
Self-expandable prosthetic devices are frequently used in a variety of treatment procedures. For example, prosthetic devices are frequently used in a variety of treatment procedures. For example, self-expandable stents are used to provide support to various vessels and ducts in the gastrointestinal system. Also, some prosthetic valves, including prosthetic venous valves, include a self-expandable support frame. In some circumstances, it may be desirable to place multiple self-expandable prosthetic devices in one or more body vessels using a single wireguide.
Accordingly, there is a need for improvements in exchangeable delivery systems and methods for expandable prosthetic devices.